Preparation of concentrated aqueous alumina suspensions for soft-molding microfabrication

This paper reports the preparation of highly concentrated aqueous alumina suspensions for demonstrating the microfabrication of ceramics by using soft molds of Poly(dimethyl siloxane) (PDMS) instead of the traditional solid molds. Zeta potential measurements showed very good dispersing effects of the dispersant NH4PAA. The rheological properties of concentrated aqueous alumina suspensions have been characterized with varying pH, NH4PAA concentration, solids loading and ultrasonic processing time. The intrinsic pH of the suspension was found suitable for molding. The optimum dispersant concentration is 0.14 wt.% and viscosities increase with more NH4PAA. A stable and easily processable suspension of 84.0 wt.% was achieved and suitable for soft-molding with viscosity of 0.30 Pa s at 100 s−1. Embossing and microtransfer molding have been used for soft-molding microfabrication and finally, crack-free and dense microstructures have been fabricated successfully with feature sizes of ∼30 μm.